Once your 360° sequence is created using a spherical image or video, you can add visual annotations using various types of media:
Images (.png, .jpg)
Hotspots (Only transparent hotspot for the moment, but other buttons will be available soon)
In order to add media to the scene of a sequence, you can simply drag and drop the media from the medialibrary onto the scene.
To create a UI at the Nadir of your project, just locate your image at a latitude of -90° and verify that the orientation selected is Sphere (not Prism). Have a look at this Gif to get all details.
See here for more information regarding orientation.
NB: It is possible to select several elements (visual annotations, texts, hotspots) by holding shift and then moving them with the keyboard arrows on the scene or with the mouse on the timeline. See this Gif for an example